BACKGROUND AND SIGNIFICANCE All four Projects in the PPG require expertise in thiol-based redox regulation and/or selenoproteins. The proposed Core C leadership has a strong track record in precisely these areas, as well as in collaborative research in general. Core C is among the few groups in the world with the necessary knowledge, expertise, instrumentation, and reagents to carry out experiments on thiol-based redox processes and selenoproteins;and has a collection of unique tools by which to do so. The Core will aid in the design of relevant experiments and their interpretation.